Combined Multi System GNSS Analysis for Time and Frequency Transfer

Transcription

1 Combined Multi System GNSS Analysis for Time and Frequency Transfer R. Dach, U. Hugentobler, T. Schildknecht, and A. Gaede Astronomical Institute, University of Bern, Sidlerstrasse 5, CH-312 Bern S. Schaer Federal Office of Topography (swisstopo), Seftigenstrasse 264, CH-384 Wabern 2th European Frequency and Time Forum (EFTF) Braunschweig, Germany, March, 27 3, 26

2 Outline Combined Multi System GNSS Analysis for Time and Frequency Transfer: 1. Motivation: Why combining multiple GNSS? 2. Description of the multi system analysis 3. Comparison of the satellite clock performance of the individual GNSS 4. Frequency dependent receiver code biases for GLONASS 5. Summary and Outlook Dach et al.: Multi System GNSS Analysis - p. 2/26

3 Multi System GNSS Analysis Number of satellites Why combining multiple GNSS? Number of observations for ONSA January total GPS GLONASS MJD Number of satellites: Dach et al.: Multi System GNSS Analysis - p. 3/26

4 Multi System GNSS Analysis General situation with multiple independent GNSS: GPS GLONASS Orbits refer to WGS 84 PZ 9 Satellite clocks refer to UTC(USNO) UTC(SU) Signal propagation dual frequency microwave systems Multipath individual for each GNSS (mainly freq. dependent) constellation repeatability one sidereal day one sidereal day ground track repeatability one sidereal day eight sidereal days Station coordinates refer to WGS 84 PZ 9 Station clocks refer to UTC(USNO) UTC(SU) Dach et al.: Multi System GNSS Analysis - p. 4/26

5 Multi System GNSS Analysis GNSS Station Distribution (used by CODE) GPS only GPS+GLONASS Dach et al.: Multi System GNSS Analysis - p. 5/26

6 Multi System GNSS Analysis Availability of GLONASS satellite clocks Dach et al.: Multi System GNSS Analysis - p. 6/26

7 Multi System GNSS Analysis G1 G2 G3 G4 G5 G6 G7 G8 G9 G1 G11 G13 G14 G15 G16 G17 G18 G19 G2 G21 G22 G23 G24 G25 G26 G27 G28 G29 G3 R1 R2 R3 R4 R7 R8 R17 R18 R19 R21 R22 R23 Redundacy for estimated satellite clocks February MJD n u m b e r o f s t a t i o n s Dach et al.: Multi System GNSS Analysis - p. 7/26

8 Multi System GNSS Analysis Satellite clock performance 1e 11 σ(τ) for (sat) SPT 1e 12 1e 13 1e Averaging time in s Legend: GPS (Block II, IIA), Cs GPS (Block II, IIA), Rb GPS (Block IIR, IIF), all Rb GLONASS GLONASS M The same stations were used to estimate the GPS and GLONASS satellite clock corrections. Dach et al.: Multi System GNSS Analysis - p. 8/26

9 Multi System GNSS Analysis (sat) SPT in ns Satellite clock performance GPS satellites of plane f February MJD G1 G13 G14 G23 G26 G29 Dach et al.: Multi System GNSS Analysis - p. 9/26

10 Multi System GNSS Analysis (sat) SPT in ns Satellite clock performance GLONASS satellites of plane a February MJD R1 R2 R3 R4 R5 R6 R7 R8 Dach et al.: Multi System GNSS Analysis - p. 1/26

11 Multi System GNSS Analysis The observations from all GNSSs are analyzed together in one parameter estimation process to get the best possible consistency for all products. GPS GLONASS Orbits refer to IGS b Satellite clocks refer to one common reference clock, or IGST Signal propagation dual frequency microwave systems Multipath individual for each GNSS (mainly freq. dependent) constellation repeatability one sidereal day one sidereal day ground track repeatability one sidereal day eight sidereal days Station coordinates refer to IGS b Station clocks refer to one common reference clock, or IGST Dach et al.: Multi System GNSS Analysis - p. 11/26

12 Receiver/Antenna Bias If such consistent products for multiple GNSS are available to the user only the biases of the users GNSS receiver/antenna remains in the data analysis. Dach et al.: Multi System GNSS Analysis - p. 12/26

13 Receiver/Antenna Bias If such consistent products for multiple GNSS are available to the user only the biases of the users GNSS receiver/antenna remains in the data analysis. Receiving signals from different GNSS with one equipment let us expect biases because of different signal structure and different frequencies that are used: Receiver antenna model Receiver intersystem, interfrequency biases Dach et al.: Multi System GNSS Analysis - p. 12/26

14 Receiver Antenna Bias Receiver antenna model Estimated corrections for GLONASS observations wrt. the GPS derived model. PCV correction in mm Elevation in degree 2 AOAD/M_B (OSOD) AOAD/M_T (JPLA) AOAD/M_T (NONE) AOAD/M_T (OSOD) ASH (DOME) 1 Dach et al.: Multi System GNSS Analysis - p. 13/26

15 Receiver Antenna Bias Receiver antenna model Estimated corrections for GLONASS observations wrt. the GPS derived model. PCV correction in mm Elevation in degree 2 AOAD/M_B (OSOD) AOAD/M_T (JPLA) AOAD/M_T (NONE) AOAD/M_T (OSOD) ASH (DOME) 1 Dach et al.: Multi System GNSS Analysis - p. 13/26

16 Receiver Antenna Bias Receiver antenna model Estimated corrections for GLONASS observations wrt. the GPS derived model. PCV correction in mm Elevation in degree 2 AOAD/M_B (OSOD) AOAD/M_T (JPLA) AOAD/M_T (NONE) AOAD/M_T (OSOD) ASH (DOME) 1 Dach et al.: Multi System GNSS Analysis - p. 13/26

17 Receiver Satellite Bias Receiver satellite biases for ONSA R24 R23 R22 R21 R19 R18 R17 R8 R7 R6 R5 R4 R3 R2 R1 G3 G29 G28 G27 G26 G25 G24 G23 G22 G21 G2 G19 G18 G17 G16 G15 G14 G13 G11 G1 G9 G8 G7 G6 G5 G4 G3 G2 G1 Dach et al.: Multi System GNSS Analysis - p. 14/ Satellite Biases in ns

18 Receiver Satellite Bias Satellite Biases in ns Receiver satellite biases for ONSA only plotted for the GLONASS satellites November 5 December 5 January 6 February 6 March MJD R1 R2 R3 R4 R5 R6 R7 R8 R17 R18 R19 R21 R22 R23 R24 Dach et al.: Multi System GNSS Analysis - p. 15/26

19 Receiver Satellite Bias Satellite Biases in ns Receiver satellite biases for ONSA only plotted for the GLONASS satellites November 5 December 5 January 6 February 6 March MJD R1 R2 R3 R4 R5 R6 R7 R8 R17 R18 R19 R21 R22 R23 R24 Dach et al.: Multi System GNSS Analysis - p. 16/26

20 Receiver Satellite Bias Receiver satellite biases for ONSA R24 R23 R22 R21 R19 R18 R17 R8 R7 R6 R5 R4 R3 R2 R1 G3 G29 G28 G27 G26 G25 G24 G23 G22 G21 G2 G19 G18 G17 G16 G15 G14 G13 G11 G1 G9 G8 G7 G6 G5 G4 G3 G2 G1 Dach et al.: Multi System GNSS Analysis - p. 17/ Satellite Biases in ns

21 Receiver Satellite Bias Receiver satellite biases for ONSA Frequency Biases in ns Frequency factor R1 R2 R3 R4 R5 R6 R7 R8 R17 R18 R19 R21 R22 R23 R24 Dach et al.: Multi System GNSS Analysis - p. 18/26

22 Receiver Satellite Bias Receiver interfrequency biases for ONSA Relative to the GPS frequencies Frequency Biases in ns Frequency factor R1 R2 R3 R4 R5 R6 R7 R8 R17 R18 R19 R21 R22 R23 R24 Dach et al.: Multi System GNSS Analysis - p. 18/26

23 Receiver Frequency Bias Receiver interfrequency biases for ASHTECH Z18 Relative to the GPS frequencies Frequency Biases in ns Frequency factor GODZ GOPE HERT JOZ2 MAT1 MTKA REUN YARR Dach et al.: Multi System GNSS Analysis - p. 19/26

24 Receiver Frequency Bias Receiver interfrequency biases for JPS LEGACY Relative to the GPS frequencies Frequency Biases in ns Frequency factor CONZ DWH1 IRKJ KHAJ KOU1 LHAZ MDVJ NOVJ REYZ SPT Dach et al.: Multi System GNSS Analysis - p. 2/26

25 Receiver Frequency Bias Receiver interfrequency biases for TPS LEGACY Relative to the GPS frequencies Frequency Biases in ns Frequency factor DARR STR2 UNB1 Dach et al.: Multi System GNSS Analysis - p. 21/26

26 Receiver Frequency Bias Receiver interfrequency biases for JPS E_GGD Relative to the GPS frequencies Frequency Biases in ns Frequency factor CAGZ OHI3 ONSA Dach et al.: Multi System GNSS Analysis - p. 22/26

27 Receiver Frequency Bias Receiver inter frequency biases for TPS E_GGD Relative to the GPS frequencies Frequency Biases in ns Frequency factor OHI3 SOFI WTZR Dach et al.: Multi System GNSS Analysis - p. 23/26

28 Geodetic GNSS Time Transfer Analysis Geodetic GNSS time transfer for ONSA SPT SPT ONSA in ns A common second order polynomial is subtracted for plotting February 6 GNSS GPS GLONASS MJD Dach et al.: Multi System GNSS Analysis - p. 24/26

29 Geodetic GNSS Time Transfer Analysis SPT ONSA in ns Differences of the time transfer solutions An offset is subtracted for plotting February 6 GPS GLONASS MJD Dach et al.: Multi System GNSS Analysis - p. 25/26

30 Summary and Outlook Summary and Outlook The consequent combined analysis of measurements from multiple GNSS guarantee the best possible consistency of the products. The performance of the GLONASS satellite clocks corresponds to the GPS block II/IIA satellites driven with Cs clocks. In the case of GPS and GLONASS no significant difference in the receiver antenna model was detected. Dach et al.: Multi System GNSS Analysis - p. 26/26

31 Summary and Outlook Summary and Outlook The GNSS receivers have not only intersystem but also interfrequency code biases that have to be considered (estimate or introduce) when analyzing GLONASS code data. The interfrequency code biases are different for individual receivers, not only for receiver types. For the carrier phase observations these biases may be absorbed by the phase ambiguity parameters. They become only relevant if the ambiguities are resolved to their integer values. As long as interfrequency code biases for the GNSS receivers have to be estimated together with the receiver and satellite clocks the advantage of more observations due to a GNSS instead of GPS analysis is compensated. The GNSS and GPS only solutions are equivalent. Dach et al.: Multi System GNSS Analysis - p. 26/26

32 Summary and Outlook Summary and Outlook The launch of more GLONASS satellites and the densification of the GNSS stations in the IGS network will improve the situation for the rigorous GNSS analysis. When adding GALILEO as the third GNSS to a combined analysis only an additional intersystem time bias for each receiver is expected. The consequent combined analysis of multiple GNSS allows the consistent processing of data from single system receivers of different GNSS as long as enough multi system receivers are available. Dach et al.: Multi System GNSS Analysis - p. 26/26